The use of roofing systems capable of successfully maintaining their integrity, particularly their ability to prevent the entry of water resulting from their exposure to rain, snow and from other causes is a fundamental requirement for any successful building structure, particularly roofing decks employed in connection with flat or low-slope roofs installed on commercial, institutional and industrial buildings.
In the past, a variety of roofing systems have been used in connection with such buildings including, for example, metal panel roofing. Such roofing usually consists of metal panels overlapped at their ends and secured to the roofing decks of building structures with nails, screws, clips or other fasteners. However, while metal panels are relatively durable, the panels are subject to significant thermally induced contractions and expansions due to ambient temperature variations, a characteristic that often leads to the cracking of such roofing, especially along the roof seams and fastener locations, with leakage occurring as a result thereof.
Another type of roofing commonly employed for such buildings is the so-called built-up roofing system. The latter type of roofing depends upon the application of asphaltic compounds to secure felt or other membranes to metal roof panels. While such systems are often used, they can be relatively expensive to provide, and again thermal contraction and expansion of the metal panels over which they are installed can result in cracking of the roof covering along its seams and fastener locations, resulting in roof leakage.
The latter type of roofing also undesirably increases the weight of the roofing surface, which can add unwanted stresses to buildings on which such roofing is installed, and in addition, the use of hot asphalt is sometimes prohibited by local building codes. Finally, built-up roofing systems typically eventually require retrofit roofing installations, and these can be difficult to provide in view of the fact that they sometimes necessitate the provision of intermediate foundation layers, such added layers creating further roofing support problems. In fact, not uncommonly, these retrofit installations can result in the shifting of the roofing deck itself, movement which causes still more cracks and further leakage.
In order to overcome the foregoing and other problems associated with such roofs, resort has increasingly been had to the use of roofing membranes formed from ethylene/propylene/non-conjugated diene rubber, EPDM, membranes. In this regard, EPDM membranes have proven to be admirably suited for roofing systems since they have a long life, substantial flexibility and retain their resiliency at very low temperatures. They are also distinguished by their ability to withstand the high temperatures frequently encountered in roofing environments without stretching or softening unduly, and by their possession of a high order of resistance to ultraviolet light. EPDM elastomers are usually blended with fillers, coloring agents, extenders, crosslinking agents and antioxidants to form compounded rubbers that are then calendared or extruded into sheets or membranes, typically about 7 to 40 feet wide, and 100 or more feet long.
In many roofing installation situations in which such membrane sheets are employed, however, it becomes necessary to overlap a number of the sheets in water-tight splices to obtain the required coverage. In one such splicing system, the procedure involves thoroughly cleaning the surface of the membranes to be joined in an overlap seam. Such cleaning is required in order to remove the talc or mica dusting used by manufacturers to keep the membrane surfaces from sticking together in the rolls in which they are marketed. Cleaning is typically done by vigorously scrubbing the surface to be joined with a rag wetted with hexane, naphtha, gasoline or some other similar material. Thereafter, a membrane adhesive, commonly consisting of a 25-30 percent, by weight, solution of rubber in a suitable solvent is brushed over the surfaces to be adhered, and following drying of the contained solvent, the surfaces are joined and pressed together to form the desired seam. In some instances, a "primer" consisting of a dilute solution of rubber in a suitable solvent is applied to the surfaces to be joined prior to application of the membrane adhesive in order to improve the final seam adhesion. Thereafter, a caulk is often added to the overlapped edges of the seam in order to protect the adhesive.
While the system described is conceptually simple, in practice, it suffers from being both labor and material intensive, and it also results in relatively low seam peel strengths. Furthermore, for environmental and health reasons, it is undesirable, and increasingly unlawful, to use a system that employs so much volatile organic compound, VOC, in the form of required components.
Partially to reduce the amount of VOC's, as well as to improve seam strengths, an alternative system has relied upon so-called seam tapes to obtain the necessary adhesion. Seam tapes, as the name implies, are sticky strips of adhesives commonly formed from butyl or other rubbers, which are compounded to include rubber tackifiers and other agents required to impart adhesive qualities.
The seaming process entails the initial cleaning of the surfaces to be joined with a liquid organic cleaner-impregnated rag to remove anti-stick dusting powders. Following such cleaning, a dilute seam primer containing from about 5 to 9 percent by weight of rubber in a solvent therefor, is applied to the membrane seam overlap surfaces, and following drying, the coated surfaces are mated and pressure is applied to the seam to secure the necessary joinder.
While the use of seam tape eliminates the VOC's which would otherwise be present as a consequence of the solvents in seam adhesives, the need to clean the surfaces with liquid organics, and the relatively large amount of solvents present in the very dilute primer make the escape of large amounts of VOC's to the atmosphere unavoidable. In addition, the need to perform both a cleaning process, as well as a priming operation, necessarily results in relatively high installation costs as a result of the additional labor and material required.
In view of the foregoing, therefore, it is a first aspect of this invention to provide a process for installing membrane roofing seams that eliminates any need to perform a separate cleaning step.
A second aspect of this invention is to provide a process for installing seams in membrane roofing systems using seam tapes that utilize primers containing lower amounts of volatile organic compound materials.
A further aspect of this invention is to provide roofing seam primers whose application to the roofing membranes obviates the needs to initially clean the surfaces to be joined.
An additional aspect of this invention is to provide roofing primers whose application to roofing membranes also serves to clean the areas of membranes to be joined.
Another aspect of this invention is to reduce the amount of volatile organic compound materials that are available to enter the atmosphere.
Yet a further aspect of this invention is to provide roofing seam primers and a method for their application that increases the peel strengths of membrane roofing seams prepared therewith.
Still another aspect of this invention is to provide a method for installing seams in membrane roofing systems that reduces installation costs, as well as the amount of fill material needed for low areas, step-offs, etc., to provide a smooth surface for receiving seam tape.